An internal combustion engine is known that is provided with a variable valve actuation device capable of varying an actuation characteristic of an intake valve. Furthermore, one such variable valve actuation device is known to allow an intake valve to be lifted in a varying amount and/or worked by a varying working angle (see PTLs 1-10).
For example, Japanese Patent Laying-Open No. 2009-202662 (PTL 1) discloses a hybrid vehicle having mounted therein an internal combustion engine having a variable valve actuation device allowing an intake valve to be lifted in an amount varying in magnitude and to be worked by a working angle (or an operation angle) varying in magnitude. PTL 1 discloses that when the hybrid vehicle has the variable valve actuation device diagnosed to have failed, and the vehicle is currently either travelling or stopped, the engine is prohibited from stopping.
Furthermore, Japanese Patent Laying-Open No. 2004-084521 (PTL 2) describes that when a means for varying timing when to open/close an intake valve and/or a means for varying a working angle on the intake valve are/is detected to have failed, the timing and/or the working angle are/is fixed and a throttle valve is also angularly controlled depending on the target intake air volume to allow for fail-safe.